Set in Los Angeles on November 30, 1962, a month after the Cuban missile crisis, A Single Man is the story of George Falconer (Colin Firth), a middle-aged English college professor who has struggled to find meaning in his life since the car accident that killed his longtime partner, Jim (Matthew Goode), eight months earlier. Jim’s family disapproved of his relationship with George and thus refused George permission to attend the funeral.

Throughout the single day depicted in the film, and narrated from his point of view, George dwells on his past, shown in flashbacks, and his seemingly empty future, as he prepares for his planned suicide that evening. He buys bullets for his revolver, empties his safety deposit box in the bank, prepares letters for some friends, and one with some money for his cleaning woman, and arranges his life insurance policy, other important things such as keys, and the clothes he wants to be dressed in by the undertaker neatly in sight. Everyday things and encounters become special for him, realizing that for each it is the last time, and he is extra nice to people, as he is secretly saying goodbye.

George makes an appointment to have dinner with his close female friend Charley (Julianne Moore). He gives a lecture, after which his student Kenny Potter (Nicholas Hoult) starts a conversation with him, and becomes fixated on him as a kindred spirit. Later George has an unexpected encounter with Spanish male prostitute Carlos (Jon Kortajarena), whom he pays while declining his services. After his dinner with Charley he encounters Kenny again in a bar. They go skinny dipping and then return to George’s house and get very drunk. George passes out and wakes to find himself in bed, with Kenny on his couch. Kenny has discovered George’s planned suicide and taken away the gun. George finds it but decides not to kill himself. Having made peace with his grief, George suffers a heart attack and dies.